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Amit Sharma, Brent A Bell, Rose M DiCicco, Nathaniel Sears, Yuankai Tao, Alex Yuan, Sunil K Srivastava; Evaluation of optical coherence tomography for measuring anterior chamber inflammation in a rabbit model of uveitis.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6186.
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© ARVO (1962-2015); The Authors (2016-present)
Anterior uveitis is an inflammatory disease of the eye which can lead to blindness. Currently, clinicians quantify anterior chamber inflammation using slit lamp biomicroscopy according to Standardization of Uveitis Nomenclature (SUN) model. Unfortunately, this method is fraught with variability. To reduce this inconsistency, we previously evaluated an automated method of quantitating cellular activity using Spectral Domain Optical Coherence Tomography (SDOCT) in humans. In this study we validate this technique in an in vivo rabbit model.
Anterior uveitis was induced by intracameral injection of Myobacterium tuberculosis H37Ra antigen in pre-immunized adult rabbits. Anterior segment OCT of each rabbit was performed and 3mm x 3mm cube scans were obtained. Hyper-reflective specks were counted by evaluating each B-scan image and the density of these specks was determined. Clinical grading of inflammation was also recorded according to SUN by 2 independent graders. Both SDOCT measurements and SUN grading were compared with the actual cell density, determined by anterior chamber sampling using a Nageotte hemocytometer (Hausser Scientific, Horsham PA).
Manual cytometry consistently yielded higher cell density counts compared with SDOCT measurements (figure 1). Cells of various sizes were found on manual cytometry, but cell clumps were rare. Both SDOCT and SUN grading correlated with manual cytometry (figures 1 and 2). However, SDOCT was better at resolving differences in cell density above ~150 cells/microliter. A reduction from 256 cells/microliter to 215.2 cells/microliter (16% reduction) was undetectable by SUN grading but resulted in a large reduction in SDOCT measured cell activity.
Our data suggests SDOCT may be a noninvasive method to objectively grade anterior chamber inflammation. Manual cytometry correlated with SDOCT counts, although the correlation is not 1:1. Thus, the hyper-reflective specks seen on OCT do not represent single cells. Faster and higher resolution imaging may be necessary to improve SDOCT measurement, especially at lower levels of inflammation.
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